pg/AsyncConnection: rename IsBusy() to IsRequestPending()

Fixes a regression by commit e6ec15f which added an IsBusy()
method which shadowed Connection::IsBusy().

src/pg/AsyncConnection.hxx

@@ -223,7 +223,7 @@ public:
 	 *
 	 * Note that this is not the strict opposite of IsIdle().
 	 */
-	bool IsBusy() const noexcept {
+	bool IsRequestPending() const noexcept {
 		return result_handler != nullptr;
 	}
 

src/pg/SharedConnection.cxx

@@ -39,7 +39,7 @@ SharedConnection::CancelQuery(SharedConnectionQuery &query) noexcept
 		   usually not idle, but maybe it's waiting for
 		   something else inbetween two queries, so we need to
 		   check anyway */
-		if (connection.IsBusy())
+		if (connection.IsRequestPending())
 			connection.RequestCancel();
 
 		/* submit the next query (outside of this caller